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Topic: Dumb question? (Read 5447 times)

I want to go FF, but loosing the length i get from a cropped body worries me. But I had a thought...

I am using a 450D (12MP) and am thinking of getting me a 5D MKIII (22MP)... If i were to crop the FF image to 12MP, what is the crop factor? 1.8 (22/12) If this is the case, with a 5D MKIII image cropped, i will actually be getting more magnification than i would with my 450D... and a lot better quality (i would hope)...

Am I barking up the wrong tree here? Am I being dumb (i'm not renown for my maths skills)?

I want to go FF, but loosing the length i get from a cropped body worries me. But I had a thought...

I am using a 450D (12MP) and am thinking of getting me a 5D MKIII (22MP)... If i were to crop the FF image to 12MP, what is the crop factor? 1.8 (22/12) If this is the case, with a 5D MKIII image cropped, i will actually be getting more magnification than i would with my 450D... and a lot better quality (i would hope)...

Am I barking up the wrong tree here? Am I being dumb (i'm not renown for my maths skills)?

You are actually correct and the quality of those pixels are different. Pixel size for 450D = 5.2µm, for 5D mark III = 6.25µm. Source: http://www.the-digital-picture.com/Reviews/Canon-EOS-5D-Mark-III-DSLR-Camera-Review.aspx. This is just looking at pixel size. Looking also at the current technology of 5D3 vs 450D, I think sensor wise, the 5D3 technology is a lot better which is also the reason why you can go for much higher ISO in 5D3 than 450D. Even the 5D2 and 5Dc(not much) are better than 450D in terms of IQ.

I want to go FF, but loosing the length i get from a cropped body worries me. But I had a thought...

I am using a 450D (12MP) and am thinking of getting me a 5D MKIII (22MP)... If i were to crop the FF image to 12MP, what is the crop factor? 1.8 (22/12) If this is the case, with a 5D MKIII image cropped, i will actually be getting more magnification than i would with my 450D... and a lot better quality (i would hope)...

Am I barking up the wrong tree here? Am I being dumb (i'm not renown for my maths skills)?

So the APSC-Crop will have a resolution of 3600 x 2400 Px which is 8.64 MP, which is less than your 12MP 450D.

To fully answer your question:

12MP -> 4272 x 2848 Px5760/4272 = 1,34

If you were to crop the FF image to 12MP the crop factor would be 1,34.(I hope i could help you a little with your maths skills )

BUT: Still the quality of the 5D3 image is so much better (sharper) that i can assure you you will not loose any detail. I had a 550D before (18MP) and upgraded to the 5D3. Since i do a lot of macro shooting i was really concerned that because of the weaker magnification the 5D3 can deliver i would obtain lesser detail. But the truth is that the images i get from 5D3 are totally crisp and sharp on pixel-level which the 550D wasn't to that extent, so i get about the same level of detail.

MPs are not the only deciding factor if you worry about IQ (or even sharpness). The 5D3 will do so much better in that regard than the 450D, you don't have to worry about losing your 'crop factor'.

I want to go FF, but loosing the length i get from a cropped body worries me. But I had a thought...

I am using a 450D (12MP) and am thinking of getting me a 5D MKIII (22MP)... If i were to crop the FF image to 12MP, what is the crop factor? 1.8 (22/12) If this is the case, with a 5D MKIII image cropped, i will actually be getting more magnification than i would with my 450D... and a lot better quality (i would hope)...

Am I barking up the wrong tree here? Am I being dumb (i'm not renown for my maths skills)?

No, but welcome to a world where you wide angle lenses are wildly expensive or wildly bad. You will cry for your 10-22 again...

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Like you math is not my strong suit, but I was wondering about the same thing as you. I have a 5D II, and my wife a 600D. I was lucky enough to borrow a 800L 5.6 and I already have the 2x III extender. So I tried to shoot the same subject first with the 1600mm combo, and then took the two lenses on my wife's camera to see how it looked at 2560mm. Although the 2560mm was closer, I realized that when I cropped hard to get as far in as I could before it started to pixelate, the same closeness of cropping with the 5D II combo (so the subject looked the same size on my screen) gave better result with the full format, as far as sharpness and patterns are concerned.

... I realized that when I cropped hard to get as far in as I could before it started to pixelate, the same closeness of cropping with the 5D II combo (so the subject looked the same size on my screen) gave better result with the full format, as far as sharpness and patterns are concerned.

I've made this point frequently - the 'reach advantage' of APS-C is an illusion from the standpoint of IQ. If you crop a FF image to the FoV of APS-C, the IQ is basically equivalent. What's not equivalent is the MP count - the images will have equivalent IQ, but the APS-C will have more MP (assuming it has a higher pixel density, and with current sensors, it will). Whether that matters or not depends on your intended use - screen viewing, web, 12x18 prints, there's no real difference. Larger prints, magazine submissions, etc., you need the MP. But in the former case, FF has no disadvantage, and if you don't need to crop, it has a definite advantage.

Photoshop and (similar applications) can be a great tool at doing this kind of math.

First, start with a full-resolution picture from each camera (you can find samples all over teh Innertubes). With the Resize Image dialog and without scaling / re-sizing / interpolating set the image size to the same physical dimensions as the camera's sensor (24mm x 36mm in the case of the 5DIII). Note: this needs to be the dimensions of the camera that took the picture, and the pixel dimensions of the picture need to remain unadulterated from when it came out of the camera.

Now, you can use the Canvas Size dialog to either crop or expand the canvas to match the physical size (not pixel dimensions) of the other camera's sensor.

What you'll see is either the amount of crop that you get plus the actual file size and resolution, or the amount of extra real estate and the file size you'd have with a larger sensor with the same pixel density.

And, at that point, you can start playing around with printing / resizing / further cropping / whatever and get a fair understanding of what that means in the real world.

No, but welcome to a world where you wide angle lenses are wildly expensive or wildly bad. You will cry for your 10-22 again...

It will be sitting on my 450D until i can get a wildly expensive WAL to go with a wildly expensive camera! Well, that would be the plan!

Thanks all for your help!

I just saw your gear list. It's VERY GOOD. So I guess it depends on how your 450D limits you. I would wait a few months to see if Canon would announce a 7DMkII and then decide. (By the way how your 450D compares to 7D in high ISO? I have NO idea but if I were to guess I would expect it to be at least equally good... )

I just saw your gear list. It's VERY GOOD. So I guess it depends on how your 450D limits you. I would wait a few months to see if Canon would announce a 7DMkII and then decide. (By the way how your 450D compares to 7D in high ISO? I have NO idea but if I were to guess I would expect it to be at least equally good... )

Yes, my 450D is the limiting factor now... ISO limitation is frustrating, AF, DR, IQ, and evening the metering is bugging me (though it has taught me a lot, since I work almost always in manual with only centre AF, focusing and recomposing).I have never had the chance to directly compare with other cameras but ISO 400 is the max (800 B&W)... 1600 is almost useless unless i get the exposure absolutely perfect, because there is little rescuing, and even then, it is mushy! From what i gather the 7D is slightly better, but not amazingly so!

I have hopes for 7D mk II, but then even if it is announced in Feb/March, it won't be available until the summer, and then will take another 6-9 months for the price to "settle"... I'm driving my little 450D into the ground (nearly 80k actuations)...

Thanks for your advice.. I do indeed have a nice set of cropped lenses... and will be sad to see them go...

There are several advantages to FF and Crop formats. Pixel density and MP are only one part of why to have each body. I agree that in post processing, cropping a FF image to a similar Crop size is a wash in terms of IQ. On the other end of the process however (clicking the shutter), where the camera matters, there is a difference. A crop body will give you more reach and allow you to compose/frame the way you wish. Cropping images after the fact can be a chore and takes quite a bit of time if you are shooting sports sequentially, etc. Depending on the crop body, it may give you superior frame rates not available in FF. My 60D has an articulating sensor that I use occasionally. The crop body may give you a better lens selection depending on your equipment. And crop bodies are less expensive than FF. If I could only have one body, it would be FF. However, I often carry two bodies and switch back and forth to have either better reach/frame rate or better width.

All I'm saying is that there is more to consider when comparing crop vs. FF besides megapixels and crop factor.